In order to join the two ends of a rubber belt together and in the process provide a strong joint therebetween, it is necessary to provide the proper heat and pressure simultaneously at the region of the joint which heat and pressure, when properly applied, act to vulcanize the rubber and thereby bond the belt ends together to form a joint. Often, in order to strengthen the joint, rubber cement is used as well as the addition of splice rubber so as to ensure that sufficient rubber is present at the region of the joint so as to provide a strong joint.
In the prior art, various methods have been utilized in order to provide heat as well as pressure at the area of the proposed joint. For example, screw jacks, hydraulic cylinders, air cylinders, etc. have been utilized in the prior art to provide the appropriate pressure for vulcanization. Further, in order to provide the proper temperature for vulcanization, electrical heating as well as steam heating have been used. Thus, in known systems, there has always been a problem with coordinating the source of pressurization with the source of heating so as to properly vulcanize the belt ends to form a proper joint.
It is desirable in pressurizing the location where the joint is to be produced to be able to uniformly pressurize the area at a pressure of between 60 and 125 psi. As noted above, one method for pressurizing the region of the splice comprises the use of screw clamps. In order to produce the required surface pressure at the area of the splice using screw clamping, it is necessary to tighten the clamp to a predetermined torque which requires expensive torque-measuring devices with the further expense incurred for paying the operator of such devices. In such an operation, a large number of screw clamps may be necessary so as to properly pressurize the entire surface area, and accordingly, it is a time consuming operation to ensure that each clamp carries its correct load. During the time that the curing of the splice takes place, it is necessary to repeatedly check each clamp so as to ensure that no relaxation of the pressure has occurred. A further problem arises from the fact that the screw clamps may only be placed along the outer edges of the belt, thus necessitating the use of transverse beams of great rigidity so as to evenly spread the pressure created by the torquing-down of the screw clamps across the surface of the splice. In order to provide sufficient rigidity in the beam so as to perform its required function, such a beam must be made quite heavy and accordingly such a beam is quite difficult to handle.
A further means known in the prior art for clamping splices comprises the use of either hydraulic or pneumatic clamps. When such systems are properly used, even surface pressure applied to the belt surfaces at the region of the splice is possible, but in order to utilize this type of clamping procedure, a large variety of additional equipment is required such as pumps, compressors, hydraulic or air cylinders and the necessary hoses and other connections. In one form of air clamping, a pressurized rubber bag is used so as to evenly distribute clamping pressure over the entire surface of the splice area and so as to enable the absorption of any undulations in the surfaces thereof. The major drawback to the use of a rubber bag is that, due to the fact that the region wherein the rubber bag is utilized is also heated to high temperatures, the lifespan of such a rubber bag is extremely limited. Further, replacing such a rubber bag is extremely expensive.
In order to vulcanize the area of the splice within a reasonable time, temperatures on the order of 300° to 360° Fahrenheit must be applied to the splice. The most commonly utilized source of heat in the splicing of rubber belts comprises radiation heating with electrical power. The main drawback to the use of electricity as a source of heat is that the site where the splicing is to take place must be within close proximity of a suitable power supply for the electricity or otherwise a large, expensive mobile electrical generator must be provided. Also, the heaters required to generate the temperatures required for vulcanization require significant voltage and, in most instances, the use of extremely long extension cables are necessary which results in large losses in voltage which thereby lowers the temperatures which may be provided through an electrical source. Thus, the time period for vulcanization may be significantly longer than what is preferred.
As stated hereinabove, a further source of heat utilized in the vulcanization of rubber comprises the use of steam. The main limitation to the use of steam appears to be the requirement for a separate boiler arrangement so as to provide the steam. However, even steam heat requires the application of pressure evenly across the area being vulcanized.
In his previous patent, U.S. Pat. No. 4,543,140, the disclosure of which is incorporated herein by reference, Applicant provided an apparatus and method for vulcanizing rubber belt splices which includes the following features:
(1) A pair of opposed steam sacks are provided, each of which is made of an extremely thin metal skin which metal may preferably be stainless steel. The thickness of the metal skin is on the order of 0.030 inches.
(2) Each steam sack is mounted on a frame device with the frame devices being reciprocable with respect to one another so as to enable adjustment of the spacing between the facing surfaces of the respective steam sacks. Thus, after the two ends of belt which are to be spliced together are placed between the steam sacks, the respective frames may be reciprocated so as to enable the engagement on opposite sides thereof by the opposed steam sacks.
(3) A boiler is provided in conjunction with the present invention which enables water to be boiled to create sufficient steam so as to pressurize the steam sacks to the desired pressure while heating them to the desired temperature simultaneously.
(4) A shut-off valve is provided in the system so that at the completion of the necessary vulcanizing time the pressurized steam may be retained within the steam sacks. The gradual cooling and condensation of the steam causes concurrent reduction in the pressure and temperature at the area of the splice to thereby allow the splice to come to a normal temperature and pressure while avoiding blistering at the region of the splice.
(5) The system includes means for adjusting the pressure of the steam within the steam sacks so as to vary the temperature to which the belt splice is exposed which thereby controls the time of vulcanization. Accordingly, the system may be adjusted to accommodate to differing widths and thicknesses of belts as well as being adjustable to provide differing vulcanization times for belts of similar characteristics.
However, even this apparatus requires the use of a heavy frame confining the steam sacks and belt ends being vulcanized together in order to obtain and maintain the necessary pressure on the relatively thin skin of the steam sacks across the area of the belt being vulcanized.
Since belt structures often require repair on site, it would be advantageous to have a vulcanizing press which is readily portable and easy to use. Thus, there is a need for a lightweight, portable, steam vulcanizing apparatus.
Various prior art devices for vulcanizing belts and similar structures are known. However, they invariably employ electrical heating together with some form of clamping apparatus which, for small applications, may be practical. For example, Serbin, U.S. Pat. No. 3,013,930, discloses an apparatus for connecting overlapped ends of a strip in which pins on an electric heating iron pass through holes in the jaws of a clamp and pierce two layers of material being joined. The pins do not perform any clamping function and are heated by the iron to melt the surrounding areas of the material being joined. The platens of the clamp structure are held closed by a spring and are indirectly heated by the iron.
Ginter, et al., U.S. Pat. No. 4,376,668, discloses an apparatus and method of making v-belts in which an electrically heated iron is clamped around the ends of a belt material in which layers of splice material have been inserted. In one embodiment, nails are inserted through the ends of the belt and splice material to hold the ends together during vulcanization, but the nails provide no clamping function.
German patent DE 2351047 discloses a vulcanizing press having rods between platen uprights which pierce a belt being joined. Electrically heated platens are positioned with the belt member between them. The patent discloses the lower platen as stationary and the upper platen as movable by pressure spindles or hydraulic cylinders. In addition to two uprights at the ends of the platens, the patent discloses several tie rods arranged between them. However, the disclosure of pressure spindles or hydraulic cylinders being used to move the upper platen raises a question as to the purpose of the tie rods. In any event, there is no means disclosed in this patent to permit the use of steam to provide heat or pressure for vulcanization in a portable apparatus. Furthermore, it appears that the pressure spindles or hydraulic cylinders provide the pressure while the tie rods appear to be for purposes of aligning the pieces being vulcanized.
For larger applications where repairs must be completed in the field, it would be preferable to have a steam vulcanizing press which does not require a heavy clamping mechanism.
Accordingly, it is a first object of the present invention to provide a lightweight portable steam vulcanizing apparatus which is simple to operate while being simple in design and assembly.
It is a further object of the present invention to provide a lightweight portable steam vulcanizing device which enables the use of steam so as to provide both pressure and heat for the vulcanization process.
It is a yet further object of the present invention to provide a lightweight portable steam vulcanizing device which enables the cooling of the vulcanized area without the use of additional equipment and while avoiding blistering of the splice.
It is a still further object of the present invention to provide a lightweight portable steam vulcanizing device which enables a smooth transition between the original material and newly vulcanized material for esthetic purposes. It is a still further object of the present invention to provide a lightweight portable steam vulcanizing device which enables the operator thereof to vulcanize a spliced area of a rubber belt with great efficiency and economy.
The foregoing objects are realized by the steam heated vulcanization apparatus of the present invention which comprises upper and lower platens comprising hollow bodies adapted to receive steam therein and transmit heat and pressure to a rubber object placed between the platens. A steam source is connected to the platens for delivery of steam and a plurality of connecting bolts pass through apertures in the platens to align the platens and secure them together so as to apply pressure to the rubber object in combination with heat.
The platens of the steam heated vulcanization apparatus comprise a rigid metal outer plate, a flexible metal inner sheet, spacers between the outer plate and the inner sheet defining a steam chamber, an inlet port releasably connectable to a steam source, and a plurality of apertures through the outer plate and the inner sheet to receive connecting bolts therethrough, the apertures having seal means whereby steam is prevented from escaping from the steam chamber.
These and other objects, aspects and features of the present invention will be better understood from the following specification when read in conjunction with the appended drawing figures.